The present invention relates generally to chains, and particularly to chains composed of a plurality of chain members each having two inner flat links that are parallel to one another, and two bushes that are rigidly disposed between the inner flat links respectively connecting two ends of same to one another. The present invention also relates to chains having outer flat links connecting the chain members in such a way that outer links, which are parallel to one another, hinge together the facing ends of two adjacent chain members with the two ends of two outer flat links connecting two chain members at each of these facing ends being rigidly connected in each case to one end of a bolt guided through and rotatably mounted to a bush.
In the re-lubrication of such chains, the lubricant is applied to the chain e.g. by drip-feed lubrication from outside. As a result of the play between the inner and outer flat links, the lubricant can also penetrate through the gap between said links and from there into the gap between the bolt and the bush. During operation, however, the play between the inner and outer flat links on several joints is set on one side and does not alter even as the chain circulates. This leads to the flow of lubricant in these joints not being optimal, such that rubbing corrosion, increased wear and premature failure of an affected joint can occur. From DE-GM 1 966 980 is known a steel flat link chain in which the outer flat links are rotatably mounted with bolts in bushes pressed securely into the inner links. In the spacing between the inner and outer flat links is provided in each case a flexible seal, through which an annular chamber lying inside the spacing is formed to receive lubricant and is sealed towards the outside together with the adjoining annular gap present between the hinge bolt and the bush. However this chain has the disadvantage that the seal, preferably consisting of plastics material, is subjected to relatively high wear and also that re-lubrication is not possible.
Furthermore, in EP 0 257 661 B1 is disclosed a roller chain to which lubricating oil can be applied, and in which the outer and inner flat links are connected to one another by means of joints consisting of bolts and sleeves and surrounded by rollers. In the peripheral direction of the roller there is provided a limited gap between at least one end face of the roller and the adjacent inner flat link and at least one radial oil feed aperture, aligned with the gap, is provided in each sleeve. In order to guarantee sufficient lubrication of the joints even under unfavourable operating conditions, the gap formed by at least one spacer element provided between the end face of the roller and the inner flat link is longer in its overall length in the peripheral direction than the peripheral extension of the spacer element or elements. This guarantees that, as a result of the relative movements between the roller and the inner flat link, the direct access to the oil feed aperture of the sleeve is exposed again and again and thus the lubricating oil can enter the gap between the bolt and the sleeve. However this chain is relatively expensive to manufacture.
It is therefore the object of the present invention to create a chain comprising chain members each having two inner flat links, parallel to one another, and two bushes rigidly disposed between the inner flat links and respectively connecting two ends of same to one another, and comprising outer flat links connecting the chain members, wherein respectively two outer flat links, parallel to one another, hinge together the facing ends of two adjacent chain members, by respectively two ends of two outer flat links connecting two chain members at each of these facing ends being rigidly connected in each case to one end of a bolt guided through a bush and rotatably mounted in same, which chain guarantees sufficient lubrication between its parts which are moveable in relation to one another, and which is simple to manufacture.
The object is achieved according to the present invention by providing bushes that protrude at their two ends beyond the outer faces of the inner flat links that face the respective outer flat link. The protrusion so formed has at least one groove-shaped lubricant passage extending from the outer diameter to the inner diameter of the bush so that lubricant can penetrate into the gap between the bolt and the bush.
Because the bushes protrude at their two ends beyond the outer faces, facing the respective outer flat link, of the inner flat links, and the protrusion so formed has at least one lubricant passage extending from the outer diameter to the inner diameter of the bush, it is guaranteed that there is constantly a sufficient distance between the facing surfaces of the inner and outer flat links and that the lubricant passage located in the gap so formed forms a non-closeable access to the annular gap between the bolt and bush for the lubricant. This effect can be maintained in a simple manner since merely the bush has to be slightly lengthened on both sides and depressions, configured preferably in the shape of grooves, have to be produced in these extensions.